What is the epic song of a group?


I will start. I vote for Stairway to Heaven for Zep. Its grand with a great finish. I will throw in Salisbury by Uriah Heap. Ok lets see some posts of what you think is a groups masterpiece.
128x128blueranger
roxy, I admit to being one who didn't take the term "epic" literally enough. I named titles which I consider epically great, but that wasn't the question. Some of mine do fit the term, such as Richard Thompson's "Shoot Out The Lights" and Television's "Marquee Moon". Here's another: Dave Edmund's reworking of Khachaturian's "Sabre Dance" when he was in the group Love Sculpture.

 Hendrix   " Voodoo Child (Slight Return)"
(Originally titled "Voodoo Chile (Slight Return)" on UK Track release)
Someone mentioned You Really Got Me for the Kinks.  I would say that was their iconic song, but I think their "epic" would be Waterloo Sunset.
Regarding Jimi Hendrix, I will have to disagree and say 1983 (a Merman I should turn to be).
For Hendrix it would have to be "Third Stone from the Sun. Starts out slow and easy. Then builds to an epic feedback solo.
Lots of great ones I see!

Pull me under - Dream Theater
Frankenstein - Edgar Winter
Snorting whiskey drinking cocaine - Pat Travers

Oh there are so many!
Awesome, keep them coming. When my Dragon comes back next week I'm going to make a mix tape of some. I bet the 20 somethings have never done that.
Queen - Bohemian Rhapsody
Clapton - Layla
Guns and roses - Paradise City
Tom Petty - American Girl
Bob Dylan - Tangled Up In Blue
Bruce Springsteen - Thunder Road

Bob Dylan: "Sad Eyed Lady Of The Lowlands". On his 1966 album Blonde On Blonde. 11:22 long, a song length unheard of at the time.

The Who: "A Quick One While He's Away". Their 1967 pre-Tommy mini-operetta, taking up one side of an LP. 

Here are some elements that I plucked of the internet to help convey the intent of my post. Don't get me wrong some of the songs members brought up are awesome and powerful.
"Epic Rock is an alternative label for Symphonic Metal and similarly grand-sounding Rock Music for North America and elsewhere that Metal is defined by a complete absence of pop elements. ... Music that sounds "epic" in addition to being Rock."   

"majestic;impressively great:the epic event"

"Oftentimes the climax at the moment where most people go "whoa...this is epic..." has an adjusted meter of some kind. Sometimes the music will go into a doubletime feel; in my opinion, this matches the human reaction of relaxation at a moment of climax. (Insert sex analogy"
My choice for another epic song would be Baba O'Reilly (aka Teenage Wasteland) by the Who. Builds slow and builds and builds till a feverish ending. Great lyrics. Epic
Ahhh here is another one. Yes "Close to the Edge" Elements of different intensties and moods. I hear several epic parts of this masterpiece. The organ and guitar solo near the middle and Jon Anderson's emotional ending. "Epic"
Iron Butterfly: In-A-Gadda-Da-Vida
Steely Dan: Hey Nineteen
Wishbone Ash: Throw Down the Sword
Yes: Starship Trooper
Allman Brothers: Whipping Post
Janis Joplin/Big Brother: Summertime
King Crimson - Court of the Crimson King AND Starless.
Yes - Close to the Edge.
Rush - 2112.
Pink Floyd - Us and Them.
Van Der Graaf Generator - A Plague of the Lighthouse Keepers.
Can - Halleluhwah.
WAR - The World is a Ghetto.
Genesis - Suppers Ready.
Lynyrd Skynyrd - Free Bird.
Mike Oldfield - Tubular Bells.
Roxy Music - Avalon.
Henry Cow - Living in the Heart of the Beast.
Zappa - Way too many to list.....
Epic... in terms of production, sound quality, songs, etc... I'd vote for two Supertramp albums:  Crime of the Century of course, but also the less appreciated (post-Hodgson) Brother Where You Bound.  Several tracks are a musical journey, and reference quality sound production.  I've heard 3 different CD pressings of "Brother" over the years, and my first edition CD from 1985 is still the most dynamic.  Get it if you can! 
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falconquest,
The question was about a group's epic song, not a list of bands. What were you thinking?
Traffic - Low Spark of High Heeled Boys
This truly Epic.

For Eric Clapton - I would say Layla even though I personally think Wonderful Tonight (about the same woman) is the better song. It's just not epic.
When I was a small boy I heard 'River Deep,Mountain High' by Tina Turner for the first time.  The melody of the song made an awesome impression on me and the hairs on my neck literally stood up.  That was a rare experience....
...don't know if you would consider Peter Gabriel as a group, but if so: 
SLEDGHAMMER!